Illumination system for a projection apparatus and projection apparatus

ABSTRACT

An illumination system and a projection apparatus adopting the illumination system are provided. The projection apparatus comprises the illumination system and a light modulator. The illumination system comprises at least one light source, a curved reflecting component, a phosphor wheel, a polarizer and a half wave retarder. The light provided by the at least one light source passes through the curved reflecting component and the phosphor wheel to provide a first light in a first time sequence and a second light in a second time sequence. The first light and the second light are transformed into a first polarized light and a second polarized light respectively in different time sequences by the polarizer and the half wave retarder.

This application claims priority under 35 U.S.C. §119 to to TaiwanPatent Application No. 101113539 filed on Apr. 17, 2012, the entirecontent of which is incorporated herein by reference.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an illumination system and a projectionapparatus adopting the illumination system, and more particularly, to anillumination system that uses a curved reflecting component incombination with a polarizer and a half wave retarder.

2. Descriptions of the Related Art

Over recent years, digital light processing (DLP) projection systemshave found a wide application in projection apparatuses because of theiradvantages, such as a high brightness, realistic colors, a rapidresponse speed and a light weight. Aside from DLP projection systemsthat are generally used to display two-dimensional (2D) images, thereare also DLP projection systems used to display stereoscopic images.

DLP projection systems for displaying stereoscopic images are generallydivided into the eyeglass type and the auto-stereoscopic type. DLPprojection systems of the eyeglass type have a low production cost andhave been widely used since the advent thereof. According to theconventional stereoscopic projection technology of the eyeglass type,two projectors are arranged in a row to simulate images visible to theleft eye and the right eye of a viewer respectively and a polarizer isinstalled in front of each of the projectors. By adjusting positions atwhich images are projected to the left eyeglass and the right eyeglass,different images will be seen at the imaging positions by the left eyeand the right eye respectively, thus achieving a stereoscopic displayingeffect.

However, in order to have the images projected by the two projectorsoverlapped at a same position, the two projectors must be alignedprecisely. Therefore, when service locations of the projectors arechanged, alignment of the two projectors must be calibrated and adjustedanew. Furthermore, use of the two projectors not only occupies a largespace but also leads to a high cost.

Accordingly, an urgent need exists in the art to design a stereoscopicimage projection apparatus that can be used with a pair of passiveeyeglasses and that has a low cost, a simplified optical arrangement anda miniaturized volume.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide anillumination system and a projection apparatus, which achieve astereoscopic displaying effect by alternately switching betweenpolarized lights with different polarization directions provided by theillumination system so that different polarized images can be seen bythe left eye and the right eye respectively. This can avoid the problemthat arrangement of two conventional projectors occupies a large areaand leads to a high cost. Another objective of the present invention isto provide an illumination system and a projection apparatus. Becausethe projection apparatus of the present invention can be used with apair of passive eyeglasses, is less costly, convenient to use and notliable to damage, the overall cost can be reduced and the convenience inuse can be improved. Furthermore, as compared to the practice of usingactive polarizers, the use of polarized lights to display stereoscopicimages can deliver a higher brightness.

Yet a further objective of the present invention is to provide anillumination system and a projection apparatus, which generate aleft-hand polarized light and a right-hand polarized light by using aquarter wave retarder in the illumination system.

To achieve the aforesaid objectives, the present invention provides anillumination system for a projection apparatus and the projectionapparatus. The projection apparatus comprises the illumination systemand a light modulator. The illumination system comprises at least onelight source, a curved reflecting component, a phosphor color wheel, apolarizer and a half wave retarder. The at least one light source isadapted to generate a light. After the light penetrates the phosphorcolor wheel in a first time sequence, a first light is reflected fromthe curved reflecting component; and after the light is reflected fromthe phosphor color wheel in a second time sequence, a second light isreflected from the curved reflecting component. The polarizer is adaptedto split the first light into a first beam having a first polarizationdirection and a second beam having a second polarization direction inthe first time sequence, and split the second light into a third beamhaving the first polarization direction and a fourth beam having thesecond polarization direction in the second time sequence. After thefirst beam and the second beam pass through a first time sequenceportion of the half wave retarder in the first time sequence, the firstbeam and the second beam are transformed into a first polarized lighthaving the first polarization direction; and after the third beam andthe fourth beam pass through a second time sequence portion of the halfwave retarder in the second time sequence, the third beam and the fourthbeam are transformed into a second polarized light having the secondpolarization direction. The light modulator is adapted to receive andtransform the first polarized light into a first view angle image in thefirst time sequence, and receive and transform the second polarizedlight into a second view angle image in the second time sequence. Then,the first view angle image and the second view angle image can bereceived by the left eye and the right eye of a user who wears a pair ofpassive eyeglasses so that a stereoscopic image is formed.

The half wave retarder of the illumination system is formed on a firstsurface of a sheet glass. The illumination system further comprises aquarter wave retarder, and the half wave retarder is disposed betweenthe quarter wave retarder and the polarizer. The quarter wave retardermay also be disposed on a second surface of the sheet glass opposite tothe first on the surface in which the half wave retarder is formed.Furthermore, the half wave retarder may also be formed on a surface of aquarter wave retarder. The at least one light source is a light emittingdiode (LED) or a laser. The illumination system further comprises alight homogenizing component to homogenize the first light and thesecond light, and the light homogenizing component is a lens array, afly lens, an integration rod, or a light tunnel. The curved reflectingcomponent comprises at least one curved surface which is an ellipsoid ora paraboloid. The curved surface has a focus, while the phosphor colorwheel is coated with at least one phosphor on the focus. The curvedsurface is coated with a light splitting coating film which only allowslights of a special waveband to pass therethrough. Furthermore, thelight modulator is a digital micromirror device (DMD) or a liquidcrystal display (LCD) panel.

The detailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an internal structure of aprojection apparatus according to an embodiment of the presentinvention;

FIG. 2A is a schematic view of a phosphor color wheel according to theembodiment of the present invention;

FIG. 2B is a schematic view of another implementation of the phosphorcolor wheel according to the present invention;

FIG. 3A is a schematic view illustrating a partial light path in a firsttime sequence according to the embodiment of the present invention;

FIG. 3B is a schematic view illustrating a partial light path in asecond time sequence according to the embodiment of the presentinvention;

FIG. 4A is a schematic view illustrating an arrangement scheme of a partof components in an illumination system of the projection apparatusaccording to the present invention; and

FIG. 4B is a schematic view illustrating another arrangement scheme of apart of components in the illumination system of the projectionapparatus according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1, 3A and 3B together, a schematic viewillustrating an internal structure of a projection apparatus accordingto an embodiment of the present invention, a schematic view illustratinga partial light path in a first time sequence and a schematic viewillustrating a partial light path in a second time sequence according tothe embodiment of the present invention are shown therein respectively.The projection apparatus 1 comprises an illumination system 11, a lightmodulator 13, a projection lens 15, a light concentrating component 17and a reflector 18. Hereinbelow, individual components of theillumination system 11 will be detailed.

The illumination system 11 comprises a light source assembly, a curvedreflecting component 111, a phosphor color wheel 112, a lighthomogenizing component 113, a polarizer 114, a half wave retarder 115, asheet glass 118 and a quarter wave retarder 119. The light sourceassembly comprises at least one light source adapted to generate alight. In this embodiment, the light source assembly comprises a firstlight source 116 and a second light source 117. The first light source116 comprises four blue laser light sources for providing four bluelaser lights simultaneously. The four blue laser lights are transformedby the curved reflecting component 111 and the phosphor color wheel 112into two red lights and two green lights (to be detailed later). Thesecond light source 117 comprises two blue light emitting diodes (LEDs)117 a, 117 b, which provide two blue lights alternately. It shall beappreciated that the first light 116 and the second light provide lightsalternately. Because solid-state light sources have been widely used inprojectors, LED light sources may also be used in place of the laserlight sources as the first light source of the present invention.

The curved reflecting component 111 has a curved surface (not labeled),and is formed with a breakthrough groove 111 a at a bottom vertexthereof. The curved reflecting component 111 has a focus definedtherein. A light splitting coating film 111 b is coated on the curvedsurface of the curved reflecting component 111 to allow only lights of aspecific waveband to pass therethrough but reflect lights of otherwavebands. In this embodiment, only blue lights are allowed to passthrough the light splitting coating film 111 b, while lights of othercolors are reflected by the light splitting coating film 111 b. In thisembodiment, the curved surface of the curved reflecting component 111 isan ellipsoid; however, in other embodiments of the present invention,the curved surface of the curved reflecting component 111 may also bereadily devised as a paraboloid by people skilled in the art.

The phosphor color wheel 112 passes through the breakthrough groove 111a of the curved reflecting component 111 with the focus of the curvedreflecting component 111 falling on the phosphor color wheel 112. Thephosphor color wheel 112 is coated with at least one kind of phosphor ina region corresponding to the focus of the curved surface of the curvedreflecting component 111. The phosphor may be coated in a circular or anannular form. Thus, the blue laser lights provided by the first lightsource 116 will be concentrated by the light concentrating component 17to the focus of the curved reflecting component 111 so that the phosphorof the phosphor color wheel 112 coated correspondingly to the focus ofthe curved reflecting component 111 will be excited and generate a redor green. Thereby, the red or green light can be intensively reflectedby the ellipsoid of the curved reflecting component 111.

In this embodiment, after the red or green light passes through thephosphor color wheel 112 in a first time sequence, a first light 10 isreflected intensively by the curved reflecting component 111. The otheralternative is that after the red or green light is reflected by thephosphor color wheel 112 in a second time sequence, a second light 12 isreflected intensively by the curved reflecting component 111.

The light homogenizing component 113 is adapted to homogenize the firstlight 10 and the second light 12. In this embodiment, the lighthomogenizing component 113 is a lens array; however, in otherembodiments, other forms of the light homogenizing component may also bereadily devised by people skilled in the art, for example, a fly lens,an integration rod or a light tunnel.

The half wave retarder 115 is disposed at a side of the polarizer 114,and is formed on a first surface of the sheet glass 118. The half waveretarder 115 has a first time sequence portion and a second timesequence portion (i.e., an upper portion 115A and a lower portion 115Bdivided by the dashed line X). The quarter wave retarder 119 is formedon a second surface of the sheet glass 118; i.e., the quarter waveretarder 119 and the half wave retarder 115 are disposed on two oppositesurfaces of the sheet glass 118 respectively. The polarizer 114 and thehalf wave retarder 115 can transform the first light 10 from theillumination system 11 into a first polarized light 14 in a first timesequence and transform the second light 12 into a second polarized light16 in a second time sequence.

It shall be appreciated that because a phase difference of a quarterwavelength is caused by the quarter wave retarder 119, a light wavealong an optic axis and a light wave perpendicular to the optic axiswill be combined into a light wave whose polarization direction canrotate. Thus, even when the view angle of a viewer shifts, the imagewill not be shielded or become blurred or incomplete.

The light modulator 13 is adapted to receive and transform the firstpolarized light 14 into a first view angle image in the first timesequence, and receive and transform the second polarized light into asecond view angle image in the second time sequence. The projection lens15 projects the first view angle image and the second view angle imageto a pair of passive eyeglasses. One of the first view angle image andthe second view angle image passes through a left eyeglass, while theother passes through the right eyeglass so that the viewer can see astereoscopic image. In this embodiment, the light modulator 3 is adigital micromirror device (DMD); however, a liquid crystal display(LCD) panel may also be used for the light modulator 3 in otherembodiments.

Now, the light paths of the lights will be detailed. First, withreference to FIG. 2A, a schematic view of the phosphor color wheel 112according to this embodiment is shown therein. As shown, the phosphorcolor wheel 112 is coated with a phosphor for exciting the blue laserlights into a red light and also a phosphor for exciting the blue laserlights into a green light. In fact, the phosphor color wheel 112 isdivided into a left portion and a right portion (which may also beunderstood as a front and a back side) for providing a red or greenlight in different time sequences. In this embodiment, the left portionthat allows a light to pass therethrough is coated in two equal halvesthereof with a phosphor for generating a red light (i.e., a region 2 rin the left portion of the phosphor color wheel 112 shown in FIG. 2A)and a phosphor for generating a green light (i.e., a region 2 g in theleft portion of the phosphor color wheel 112 shown in FIG. 2A); andsimilarly, the right portion that reflects a light is coated in twoequal halves thereof with a phosphor for generating a red light (i.e., aregion 2 r′ in the right portion of the phosphor color wheel 112 shownin FIG. 2A) and a phosphor for generating a green light (i.e., a region2 g′ in the right portion of the phosphor color wheel 112 shown in FIG.2A). From this concept, other implementations of phosphor coating mayalso be devised by people skilled in the art. For example, as shown inFIG. 2B, the left portion and the right portion are transmissive andreflective respectively, and are each coated with phosphors forgenerating a red light, a green light and a yellow light (i.e., regions2 r, 2 g and 2 y as well as 2 r′, 2 g′ and 2 y′ of the phosphor colorwheel 112′ shown in FIG. 2B). Likewise, the left portion and the rightportion further have a region that is transmissive and reflective for ablue light respectively (i.e., a region 2 b and a region 2 b′ of thephosphor color wheel 112′ shown in FIG. 2B). In order for image colorsgenerated subsequently to satisfy the requirements, percentages of theseregions are different.

Transformation of lights in the illumination system 11 will be furtherdetailed as follows. Still, with reference to FIG. 1, in the embodimentof the present invention, the blue laser lights are first concentratedby the light concentrating component 17 located at a back end of thefirst light source 116 to the focus of the curved reflecting component111. In the first time sequence, the blue laser lights from the firstlight source 116 are projected onto the transmissive left portion of thephosphor color wheel 112 to excite generation of a red and green lightrespectively at different time points, and then the red or green lightis concentrated by the curved surface of the curved reflecting component111 into a first light 10; and in the second time sequence, the bluelaser lights from the first light source 116 are projected onto thereflective right portion of the phosphor color wheel 112 to excitegeneration of a red and green light respectively at different timepoints. The red or green light is concentrated by the curved reflectingcomponent 111 into a second light 12.

In the first time sequence, the first light 10 is reflected by thereflector 18 into the light homogenizing component 113; and in thesecond time sequence, the second light 12 is also reflected by thereflector 18 into the light homogenizing component 113. In thisembodiment, because the use of the curved reflecting component 111 makesthe first light and the second light travel along different light paths,the first light 10 reflected by the reflector 18 will be processed by anupper half of the subsequent optical components in the illuminationsystem 11, while the second light 12 reflected by the reflector 18 willbe processed by a lower half of the subsequent optical components in theillumination system 11. The subsequent optical components describedherein at least include the light homogenizing component 113, thepolarizer 114, the half wave retarder 115, the sheet glass 118 and thequarter wave retarder 119.

The first light source 116 and the second light source 117 providelights simultaneously. Therefore, after the first light 10 (which ismade of a red and green light and is excited by the phosphor color wheel112) is provided by the first light source 116 in the first timesequence and reflected intensively by the curved reflecting component111, a blue light is provided by the blue LED 117 a of the second lightsource 117, also in the first time sequence and travels along the samelight path as the first light 10. On the other hand, after the secondlight 12 (which is made of a red and green sequentially and is excitedby the phosphor color wheel 112) is provided by the first light source116 in the second time sequence and reflected intensively by the curvedreflecting component 111, a blue light is also provided by the blue LED117 b of the second light source 117 in the second time sequence andtravels along the same light path as the second light 12. In otherwords, the phosphor color wheel 112 cooperates with the first lightsource 116 and the blue LED 117 a to provide a red light, a green lightand a blue light sequentially in the first time sequence, and cooperateswith the first light source 116 and the blue LED 117 b to provide a redlight, a green light and a blue light sequentially in the second timesequence. However, as will be readily appreciated by people skilled inthe art, the sequence of color lights provided in the present inventionis not limited to what has been illustrated above.

Next, the propagation of lights in the different time sequences will bedescribed. FIGS. 3A and 3B show schematic views of light paths in thepolarizer 114, the half wave retarder 115, the sheet glass 118 and thequarter wave retarder 119 of the aforesaid embodiment corresponding tothe first time sequence and the second time sequence respectively.

In detail, as shown in FIG. 3A, the first light 10 (which is a redlight, a green light or a blue light at different time points) is splitby the upper portion of the polarizer 114 into a first beam 14 s with afirst polarization direction and a second beam 14 p with a secondpolarization direction in the first time sequence. The first beam 14 swith the first polarization direction is generated through thereflection by a polarization coating film of the polarizer 114, whilethesecond beam 14 p with the second polarization direction transmitsthrough the polarization coating film of the polarizer 114. Then, onlythe second beam 14 p with the second polarization direction passesthrough the upper first time sequence portion of the half wave retarder115 and is then transformed into a light beam also with the firstpolarization direction. Therefore, the first polarized lights 14 passingthrough the sheet glass 18 both have the first polarization directionwhich, in this embodiment, is the S polarization direction.

As shown in FIG. 3B, the second light 12 (which is a red light, a greenlight or a blue light at different time points) is split by the lowerportion of the polarizer 114 into a third beam 16 s with the firstpolarization direction and a fourth beam 16 p with the secondpolarization direction in the second time sequence. The third beam 16 swith the first polarization direction is generated through reflection bythe polarization coating film of the polarizer 114, while the fourthbeam 16 p with the second polarization direction transmits through thepolarization coating film of the polarizer 114. Then, only the thirdbeam 16 s with the first polarization direction passes through the lowersecond time sequence portion of the half wave retarder 115 and is thentransformed into a light beam also with the second polarizationdirection. Therefore, the second polarized lights 16 passing through thesheet glass 118 both have second polarization directions which, in thisembodiment, is the P polarization direction.

It shall be noted that to transform lights with different polarizationdirections into a same polarization direction, the size of the half waveretarder 115 disposed at the back of the polarizer 114 must coordinatewith an angle of the polarization coating film of the polarizer 114.

Additionally, the polarizer 114 and the half wave retarder 115 split thelight into two polarized lights with different polarization directions,namely, a polarization direction along the optic axis and a polarizationdirection perpendicular to the optic axis. When a viewer's head tilts(i.e., when the pair of passive eyeglasses is not completely alignedwith the polarization directions), it is very likely that the first viewangle image and the second view angle image will transmit through theleft eyeglass and the right eyeglass simultaneously and cause blurringof the images.

To avoid the occurrence of this problem, a quarter wave retarder 119 isdisposed at a back end of the half wave retarder 115 in this embodiment.The half wave retarder 115 and the quarter wave retarder 119 togetherform a circular polarizer or an elliptical polarizer. Generally, thecircular polarizer or the elliptical polarizer consisting of the halfwave retarder 115 and the quarter wave retarder 119 may further dividethe light into a left-hand polarized light or a right-hand polarizedlight, but the present invention has no limitation thereon.

FIGS. 4A and 4B show schematic views of different arrangement schemes ofthe polarizer, the half wave retarder, the sheet glass and the quarterwave retarder of the present invention respectively. As shown in FIG.4A, the half wave retarder 43, the sheet glass 45 and the quarter waveretarder 47 are all disposed at a side of the polarizer 41, with thehalf wave retarder 43 being formed on a first surface of the sheet glass45 and the quarter wave retarder 47 being formed on a second surface ofthe sheet glass 45 opposite to the half wave retarder 43. Alternatively,as shown in FIG. 4B, the half wave retarder 43, the sheet glass 45 andthe quarter wave retarder 47 are all disposed at a side of the polarizer41, with the half wave retarder 43 being formed directly on the quarterwave retarder 47 and the other side of the quarter wave retarder 47being attached onto the sheet glass 45.

According to the above descriptions, the primary objective of theillumination system and the projection apparatus adopting theillumination system of the present invention is to switch betweenleft-hand polarized lights and right-hand polarized lights provided bythe illumination system in different time sequences alternately so thatdifferent polarized images can be seen by the left eye and the right eyerespectively to achieve a stereoscopic displaying effect. This can avoidthe problem that arrangement of two projectors occupies a large area andleads to a high cost. As another objective, the illumination system andthe projection apparatus of the present invention can be used with apair of inexpensive eyeglasses and are not liable to damage, so theoverall cost can be reduced. Furthermore, as compared to the practice ofusing active polarizers, the use of polarized lights to displaystereoscopic images can deliver a higher brightness. Moreover, becauseof the reduced cost, the illumination system and the projectionapparatus of the present invention are suitable for use in large-scaleservice places.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

What is claimed is:
 1. An illumination system for a projectionapparatus, comprising: at least one light source for generating a light;a curved reflecting component having a breakthrough groove; a phosphorcolor wheel being disposed in the breakthrough groove, wherein after thelight penetrates the phosphor color wheel in a first time sequence, afirst light is reflected from the curved reflecting component, and afterthe light is reflected from the phosphor color wheel in a second timesequence, a second light is reflected from the curved reflectingcomponent; a polarizer for splitting the first light into a first beamhaving a first polarization direction and a second beam having a secondpolarization direction in the first time sequence, and splitting thesecond light into a third beam having the first polarization directionand a fourth beam having the second polarization direction in the secondtime sequence; and a half wave retarder having a first time sequenceportion and a second time sequence portion, and being disposed at a sideof the polarizer; wherein after the first beam and the second beam passthrough the first time sequence portion of the half wave retarder in thefirst time sequence, the first beam and the second beam are transformedinto a first polarization light having the first polarization direction,and after the third beam and the fourth beam pass through the secondtime sequence portion of the half wave retarder in the second timesequence, the third beam and the fourth beam are transformed into asecond polarization light having the second polarization direction. 2.The illumination system as claimed in claim 1, wherein the half waveretarder is formed on a first surface of a sheet glass.
 3. Theillumination system as claimed in claim 1, further comprising a quarterwave retarder, and the half wave retarder is disposed between thequarter wave retarder and the polarizer.
 4. The illumination system asclaimed in claim 1, further comprising a quarter wave retarder disposedon a second surface of the sheet glass opposite to the first surface onwhich the half wave retarder is formed.
 5. The illumination system asclaimed in claim 1, wherein the half wave retarder is formed on asurface of a quarter wave retarder.
 6. The illumination system asclaimed in claim 1, wherein the at least one light source is a lightemitting diode (LED) or a laser.
 7. The illumination system as claimedin claim 1, further comprising a light homogenizing component tohomogenize the first light and the second light, and the lighthomogenizing component is a lens array, a fly lens, an integration rod,or a light tunnel.
 8. The illumination system as claimed in claim 1,wherein the curved reflecting component comprises at least one curvedsurface which is an ellipsoid or a paraboloid.
 9. The illuminationsystem as claimed in claim 8, wherein the curved surface has a focus,and the phosphor color wheel is coated with at least one phosphor on thefocus.
 10. The illumination system as claimed in claim 8, wherein thecurved surface is coated with a light splitting coating film which onlyallows lights of a special waveband to pass therethrough.
 11. Aprojection apparatus, comprising: an illumination system as claimed inclaim 1, the illumination system providing the first polarized light inthe first time sequence and providing the second polarized light in thesecond time sequence; and a light modulator for receiving andtransforming the first polarized light into a first view angle image inthe first time sequence and receiving and transforming the secondpolarized light into a second view angle image in the second timesequence.
 12. The projection apparatus as claimed in claim 11, whereinthe light modulator is a digital micromirror device (DMD) or a liquidcrystal display (LCD) panel.